Main Session

Sep 29

PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care

3454 - Recurrence Patterns Relative to Residual Tumor after Induction Chemotherapy in Nasopharyngeal Carcinoma

03:45pm - 05:00pm ET

Poster Hall - Exhibit Hall A

Screen: 6

POSTER

Presenter(s)

Peng Ding, MBBS - Jiang Xi Province Cancer Hospital, Nanchang, JiangXi Province

P. Ding^1,2, X. Sun¹, and H. Liao³; ¹JiangXi Medical College,Nanchang University, Nanchang, China, ²Department of Radiation Oncology, Jiangxi Cancer Hospital, Second Affiliated Hospital of Nanchang Medical College, Nanchang, China, ³Jiangxi Medical College, Nanchang University, Nanchang, China

Purpose/Objective(s):

To characterize spatial patterns of locoregional recurrence in nasopharyngeal carcinoma (NPC) treated with induction chemotherapy (IC) followed by concurrent chemoradiotherapy. Unlike prior studies that primarily evaluated recurrence relative to planning target volumes (PTVs), this study specifically investigated whether recurrent tumors originated from residual disease after IC and explored the association between tumor regression response and recurrence patterns.

Materials/Methods:

A retrospective analysis was conducted on 31 patients with locally advanced NPC who developed locoregional recurrence after IC followed by intensity-modulated radiotherapy (IMRT) with concurrent chemotherapy between 2016 and 2022. Pre-treatment MRI, post-IC MRI, and recurrence MRI were rigidly registered to planning CT using the Varian Eclipse system. Recurrent gross tumor volumes were delineated based on diagnostic imaging and multidisciplinary consensus. Spatial relationships between recurrence sites and both pre-IC and post-IC tumor volumes were evaluated. Dosimetric assessment was performed using dose-volume histograms (DVHs). Recurrence patterns were classified according to the proportion of recurrent volume covered by the post-IC primary PTV receiving =95% of the prescribed dose.

Results:

The median follow-up was 58 months, and the median time to recurrence was 28 months. The mean tumor regression after IC was 23.8%. Most recurrences occurred in the nasopharynx (83.9%) and skull base (54.8%). In-field recurrence accounted for 22/31 (67.7%) of cases, and 27/31 (87.1%) of recurrence centers were located within the post-IC residual tumor volume. Notably, 22/31 patients (70.9%) demonstrated tumor regression =25% following IC. Recurrent disease predominantly originated from areas of persistent residual tumor after induction treatment.

Conclusion:

Locoregional recurrence after IC-based chemoradiotherapy in NPC predominantly arises from residual tumor regions that persist following induction treatment. Limited tumor regression (=25%) was common among recurrent cases, suggesting that inadequate response to IC may be associated with subsequent local failure. These findings support further investigation of response-adapted treatment strategies and biologically guided dose intensification for high-risk residual disease.